Diesel engines in certain motor vehicles often use a starting aid, particularly when engine starting is attempted in cold weather. The starting aid is employed until sufficient heat has been developed in the combustion chambers for assured combustion of injected diesel fuel by compression ignition.
Known cold start aids include ether injection, block heating, and glow plugs. Ether injection introduces into the combustion chambers a gas (ether) that is highly combustible and effective to aid fuel ignition even at low temperatures. The use of ether requires an on-board supply that eventually needs to be replenished, and installation of an ether system adds to the engine cost.
Glow plugs are electrically energized to heat the combustion chambers to aid combustion of injected diesel fuel. After an initial period of being energized before the engine is cranked, the glow plugs may continue to be energized for a limited time as the engine begins to run.
A glow plug starting aid system typically has one or more glow plugs associated with each combustion chamber, and some form of controller or control system that controls the delivery of electric current to the glow plugs from the vehicle battery or battery bank. The controller may comprise one or more relays or solid state devices through which battery current is conducted to the glow plugs.
When a cold engine is to be started, one or more relays operate one or more contacts that connect the glow plugs to the battery, with the electric current acting to heat the glow plugs which in turn heat the combustion chambers. During combustion chamber heating the relays may be intermittently cycled off by the controller so that the current is intermittently delivered to the glow plugs. The engine is thereafter cranked until it starts and begins running under its own power, and the relays may continue to be operated for a limited length of time as the engine warms up.
Failure of a cold start aid to start the engine may be due to various causes including ones other than in the cold start aid itself. In cold weather, a fault in the cold start aid may be sufficient by itself however to render the engine incapable of being successfully started. Cold weather also strains the battery or batteries that are used to crank the engine via the starter motor. A driver of a motor vehicle who is attempting to start a diesel engine in cold weather may continue cranking the engine in expectation of its eventual starting. But excessive cranking will drain the battery or batteries and render them incapable of further cranking. At that point, the vehicle requires service personnel and equipment to come to its aid, often resulting in the vehicle having to be towed to a service facility.
A known glow plug start aid comprises a glow plug module, or controller, that is installed in a motor vehicle in association with the engine. The start aid may be essentially entirely self-contained in the module except of course for the glow plugs themselves. Diagnostics can be included for indicating an under- or non-performing glow plug.